The
average of 5 numbers is 7. When 3 new numbers are added, the average of the 8
numbers is 8.5. The average of the 3 new numbers is:

Solution:

Sum of 3 new numbers = (8 ×8.5) -
(5 × 7) = 33

∴Their average = 33/3 =
11

Example:
02

A
cricketer has a certain average for 9 innings. In the tenth inning, he scores
100 runs, thereby increasing his average by 8 runs. His new average is:

Solution:

Let, average of 9 innings be x

Then, (9x + 100)/10 = x + 8

or,
10x + 80 = 9x + 100

or,
x = 20

∴The new average is = (x
+ 8) = 28 runs.

Example:
03

In a cricket team, the average of 11
players is 28 years. Out of these, the average ages of 3 groups of 3 players
each are 25 years, 28 years and 30 years respectively. If in these groups, the
captain and the youngest player are not included and the captain is 11 years
older than the youngest player. What is the age of the captain?